Frequencies for first 10,000 rows of injury variable in nhamcsed2013 dataset :

       Is visit related to |
      injury, poisoning or |
 adverse effect of medical |
             treatment? -  |      Freq.     Percent        Cum.
---------------------------+-----------------------------------
                     Blank |         92        0.92        0.92
                   Unknown |        270        2.70        3.62
                        No |      6,251       62.51       66.13
                       Yes |      3,367       33.67       99.80
Questionable injury status |         20        0.20      100.00
---------------------------+-----------------------------------
                     Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016